Child Theme Problems

Hello,

I purchased a child theme of TwentyTwelve some days ago, well I’m having some problems with it.

I actually would like to change some things about the comment form and the single page, since there isn’t a comments.php or a single.php I thought it would be fine to just place the files.

So I copied the comments.php inside the child theme folder, but nothing happened. I did saw it in the Editor but it was empty and when I copied something inside the file, no changes were actually visible.

Now, I really would like to figure out what’s the point about it and how to fix this issue.

I hope someone here might have an idea, thanks!